[PATCH 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function

[Jeremy Linton]

From: Mian Yousaf Kaukab <ykaukab@xxxxxxx>

Add is_meltdown_safe() which is a whitelist of known safe cores.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@xxxxxxx>
[Moved location of function]
Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
---
 arch/arm64/kernel/cpufeature.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index aec5ecb85737..242898395f68 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -908,8 +908,7 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope)
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */
 
-static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
-				int scope)
+static bool is_cpu_meltdown_safe(void)
 {
 	/* List of CPUs that are not vulnerable and don't need KPTI */
 	static const struct midr_range kpti_safe_list[] = {
@@ -917,6 +916,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
 		{ /* sentinel */ }
 	};
+	/* Don't force KPTI for CPUs that are not vulnerable */
+	if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+		return true;
+
+	return false;
+}
+
+static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
+				int scope)
+{
 	char const *str = "command line option";
 
 	/*
@@ -940,8 +949,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
 		return true;
 
-	/* Don't force KPTI for CPUs that are not vulnerable */
-	if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
+	if (is_cpu_meltdown_safe())
 		return false;
 
 	/* Defer to CPU feature registers */
-- 
2.17.2